Light photomicrographs of two morphotypes of Demidospermus anus parasite of L. platymetopon from Upper Paraná River floodplain, Paraná, Brazil. A and B – ventral and dorsal bars and anchors (morphotype A), respectively. C and D – ventral and dorsal bars and anchors (morphotype B), respectively, in detail, the joint point in the ventral bar evidencing the sclerotized narrowing. E – vagina (morphotype A). F – vagina (morphotype B). G – sclerotized distal portion of the deferens duct (morphotype A). H – sclerotized distal portion of the deferens duct (morphotype B). I – MCO: accessory piece (AP); base of the MCO (BMCO) (morphotype A). J – MCO (morphotype B). Scale bar = 100 µm (A), 20 µm (A–D, G–H), 10 µm (E–F, I–J).